Retro-Reflective Light Diffusing Display Systems

ABSTRACT

Aspects of the present invention involve novel display screens comprising light diffusion and retro-reflectivity. In embodiments, a retro-reflective light diffusion screen can be used to generate a three-dimensional autostereoscopic display by generating a plurality of viewing windows wherein each viewing window depicts a unique perspective image view. In embodiments, the retro-reflective light diffusion screen comprises a transparent medium layer between the retro-reflector surface and the light diffuser layer to help reduce ghost images. In embodiments, the retro-reflective light diffusion screen comprises a lenticular layer positioned such that the light diffuser layer is between the lenticular layer and the retro-reflective surface and is also positioned so that the light diffuser layer is at a focal plane of the lenticular layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of and claims the benefit ofco-pending and commonly assigned U.S. patent application Ser. No.12/418,137, entitled “RETRO-REFLECTIVE LIGHT DIFFUSING DISPLAY SYSTEMS,”which was filed on Apr. 3, 2009, and lists Chunyu Gao and Jing Xiao asinventors. The entirety of the aforementioned application is hereinincorporated by reference.

BACKGROUND

A. Technical Field

The present invention pertains generally to displays, and relates moreparticularly to autostereoscopic three-dimensional (3D) displays.

B. Background of the Invention

Three-dimensional movies and television are becoming increasingly morepopular. With advances in technology, such as high-definition (HD)television, consumers desire more and better features. According to the“2008 3D Television Report” released in May 2008 by Insight Media, 3Dmay soon be an add-on feature of high-definition television. Manydisplay manufacturers are developing their own 3D display technologiesto meet these market demands.

In the current 3D market, traditional standard two-view stereo remainsas the dominant implementation. For example, head mounted displays arewidely used in the military training and research community, glass-basedprojection displays play a key role in the large form 3D display, suchas the CAVE® system and PowerWall systems of Mechdyne Corporation, aswell as 3D cinemas. However, the requirement of wearing a helmet orglasses limits the use of the 3D technologies. As an alternativesolution, autostereoscopic display technologies have attractedincreasing attention. Autostereoscopic displays use special lightdirecting devices to create separate viewing windows in the user'sspace, which allow the user to see 3D images without glasses. Since thedesignated viewing windows form a viewing space which is significantlylarger than the size of the human eye, users can move their heads freelyas long as their eyes are within the viewing space.

Current stereoscopic methods used to produce the viewing windows includeparallel-barrier-based displays and lenticular-based displays. However,these autostereoscopic display technologies have significant limitation.

For example, parallel-barrier-based displays suffer from severallimitations. First, because parallel-barrier displays use light blockingto produce viewing windows, only a small amount of light emitted fromeach pixel passes through the barrier window. Second, crosstalk betweenviews can be significant. Crosstalk refers to the overlap of viewingareas, which results when one eye sees the image intended for the othereye. When the crosstalk is significant, the brain cannot perceive thestereo effect or cannot perceive it correctly. Third, the use of smallapertures in parallel-barrier-based displays can cause diffraction. Thisproblem becomes more acute as the display resolution increases. As thedisplay resolution increases, the barrier aperture size must bedecreased, which causes more severe diffraction effects. Fourth,parallel-barrier-based displays typically suffer from limitedresolution. For a display with n views, the resolution of the individualview is essentially 1/n of the original display resolution. Because theviews have to divide the resolution of the original display, aparallel-barrier-based display's resolution is limited by the originalresolution of the display, which is also limited by diffraction as wellas the display manufacturer's capability. Fifth, since each view onlysees one pixel column out of n associated with one barrier window, thereare many dark pixels lines in each view, which creates a “picket fenceeffect” in the monocular image. Finally, parallel-barrier-based displaystypically suffer from having a limited number of viewing windows. Inorder to generate more viewing windows, the dark slits have to be widerwhile the slit windows remain unchanged. Obviously, it is impossible toinfinitely increase the number of viewing windows without aggregatingthe artifacts such as reduced brightness and picket fence effect.

Although lenticular-based displays offer some improvements overparallel-barrier-based displays, the use of lenticular sheets also hasimportant drawbacks. Lenticular-based displays offer higher resolutioncompared with barrier slits; however, it is more difficult and costly tomake high quality lenticular sheets than to make simple black-whitebarriers. In fact, the quality of the display is directly related to thequality of the lenticular sheet used in the display. Aligning alenticular sheet with a display also requires significant effort.Furthermore, lenticular-based displays also suffer from problems thatplague parallel-barrier-based displays, such as crosstalk between viewwindows, dark line problem, limited resolution, and limit number ofviewing windows.

SUMMARY OF THE INVENTION

Accordingly, what is needed are systems and methods that provide betterdisplays, particularly better displays that can be used forautostereoscopic displays.

Aspects of the present invention involve the use of light diffusion andretro-reflectivity to generate novel display screens. In embodiments, aretro-reflective light diffusion screen can be used to generateautostereoscopic displays by generating a plurality of viewing windows.In embodiments, each viewing window depicts a perspective image view anda 3D image can be views by viewing one perspective image view from oneviewing window with one eye and by viewing another perspective imageview from another viewing window with the other eye.

In embodiments, a display screen system comprising a screen that has atwo-dimensional retro-reflective surface and a diffusion surface. Thediffusion surface is configured with a large diffusion angle in a firstdirection and a small diffusion angle in a second direction. For thedisplay screen, the first direction is preferably the vertical directionand the second direction is preferably the horizontal direction. Thediffusion surface is also configured to receive an image reflected fromthe two-dimensional retro-reflective surface and to diffuse the image toform a viewing window corresponding to the image.

In embodiments, a display screen system comprises a retro-reflectordiffuser screen and at least one additional layer. In embodiments, theadditional layer may be a transparent layer between the two-dimensionalretro-reflector and the light shaping diffuser. In embodiments, theadditional layer may be a lenticular layer that is positioned in frontof the light shaping diffuser. In yet other embodiments, theretro-reflector diffuser screen comprises a lenticular layer, a lightshaping diffuser, a transparent medium layer, and a two-dimensionalretro-reflector.

The display screen system can also include a plurality of projectors.Each projector has a unique position and is configured to project animage with a unique perspective view onto the screen to form a uniqueviewing window corresponding to the projected image. Thus, the displaysystem forms a plurality of viewing windows corresponding to a pluralityof images projected by the plurality of projectors. A user can view athree-dimensional image by viewing a first perspective image with oneeye at a first viewing window selected from the plurality of viewingwindows and by viewing a second perspective image with the other eye ata second viewing window from the plurality of viewing windows.

In embodiments, the display screen system also comprises a beamsplitterpositioned in an optical path between at least one of the plurality ofprojectors and the screen to direct a projected image to the screen andto direct the projected image reflected from the screen to a location toform a viewing window that is spatially separate from the at least oneof the plurality of projectors. Such configurations remove the projectoras an obstacle in the viewing window.

In embodiments, the display system also includes a second screenretro-reflective light diffusing screen positioned at an opticallymirror-conjugated position relative to the first screen to increase thebrightness of the image at a viewing window.

In embodiments, the display system includes a polarization-sensitivebeamsplitter positioned in an optical path between at least one of theplurality of projectors and the screen to direct a projected image tothe screen and a quarter-wave plate positioned in an optical pathbetween the screen and the beamsplitter.

In embodiments, the display system includes a computing devicecommunicatively coupled to the plurality of projectors to coordinateprojection of images. The computing device may also include one or moredatastores for storing images to be projected. It should be noted thatthe images to be projected may be still images, video images, or both.

Embodiments of the present invention also include methods for making anautostereoscopic display system according to teachings presented herein.For example, in embodiments, an autostereoscopic display system can beformed by positioning a retro-reflective light diffusing screen toreceive projected images from a plurality of projectors. Each projectorhas a unique position and is configured to project an image with aunique perspective view onto the screen to form a viewing windowcorresponding to the projected image. A plurality of viewing windows areformed corresponding to the plurality of images projected by theplurality of projectors. The plurality of viewing windows are positionedsuch that a user can view a three-dimensional image by viewing a firstperspective image with one eye at a first viewing window selected fromthe plurality of viewing windows and by viewing a second perspectiveimage with another eye at a second viewing window.

Some features and advantages of the invention have been generallydescribed in this summary section; however, additional features,advantages, and embodiments are presented herein or will be apparent toone of ordinary skill in the art in view of the drawings, specification,and claims hereof. Accordingly, it should be understood that the scopeof the invention shall not be limited by the particular embodimentsdisclosed in this summary section.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made to embodiments of the invention, examples ofwhich may be illustrated in the accompanying figures. These figures areintended to be illustrative, not limiting, and are also not drawn toscale. Although the invention is generally described in the context ofthese embodiments, it should be understood that it is not intended tolimit the scope of the invention to these particular embodiments.

FIG. 1 illustrates the operation of a light diffusion screen accordingto various embodiments of the invention.

FIG. 2 illustrates the operation of a retro-reflective screen accordingto various embodiments of the invention.

FIG. 3 illustrates the operation of a retro-reflective vertical lightdiffusion screen according to various embodiments of the invention.

FIG. 4 illustrates a display system with a retro-reflective verticallight diffusion screen according to various embodiments of theinvention.

FIG. 5 illustrates a multi-projector display system with aretro-reflective vertical light diffusion screen according to variousembodiments of the invention.

FIG. 6 illustrates an alternative embodiment of a display system with aretro-reflective vertical light diffusion screen according to variousembodiments of the invention.

FIG. 7 illustrates another embodiment of a display system with at leastone retro-reflective vertical light diffusion screen according tovarious embodiments of the invention.

FIG. 8 illustrates yet another embodiment of a display system with aretro-reflective vertical light diffusion screen according to variousembodiments of the invention.

FIG. 9 illustrates another embodiment of a retro-reflective lightdiffusion screen according to various embodiments of the invention.

FIG. 10 illustrates the retro-reflective light diffusion screen of FIG.9 according to various embodiments of the invention.

FIG. 11 illustrates an example of a lenticular reflection screen.

FIG. 12 illustrates another embodiment of a retro-reflective lightdiffusion screen with a lenticular layer according to variousembodiments of the invention.

FIG. 13 depicts the light distribution of a view window from anembodiment of a retro-reflective light diffusion screen according tovarious embodiments of the invention.

FIG. 14 depicts the cross-section of two adjacent view windows from anembodiment of a retro-reflective light diffusion screen according tovarious embodiments of the invention.

FIG. 15 illustrates yet another embodiment of a retro-reflective lightdiffusion screen according to various embodiments of the invention.

FIG. 16 illustrates a multi-projector display system with at least oneembodiment of a retro-reflective light diffusion screen according tovarious embodiments of the invention.

FIG. 17 depicts a block diagram of an example of a computing systemaccording to embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, for purposes of explanation, specificdetails are set forth in order to provide an understanding of theinvention. It will be apparent, however, to one skilled in the art thatthe invention can be practiced without these details. Furthermore, oneskilled in the art will recognize that embodiments of the presentinvention, described below, may be implemented in a variety of ways.Accordingly, the examples described below are illustrative of specificembodiments of the invention and are meant to avoid obscuring theinvention.

Components, or modules, shown in block diagrams are illustrative ofexemplary embodiments of the invention and are meant to avoid obscuringthe invention. It shall also be understood that throughout thisdiscussion that components may be described as separate functionalunits, which may comprise sub-units, but those skilled in the art willrecognize that various components, or portions thereof, may be dividedinto separate components or may be integrated together, includingintegrated within a single system or component.

Furthermore, connections between components within the figures are notintended to be limited to direct connections. Rather, data between thesecomponents may be modified, re-formatted, or otherwise changed byintermediary components. Also, additional or fewer connections may beused. It shall also be noted that the terms “coupled” or“communicatively coupled” shall be understood to include directconnections, indirect connections through one or more intermediarydevices, and wireless connections.

Reference in the specification to “one embodiment,” “preferredembodiment,” “an embodiment,” or “embodiments” means that a particularfeature, structure, characteristic, or function described in connectionwith the embodiment is included in at least one embodiment of theinvention and may be in more than one embodiment. The appearances of thephrases “in one embodiment,” “in an embodiment,” or “in embodiments” invarious places in the specification are not necessarily all referring tothe same embodiment or embodiments. It shall also be understood that theterms “image” or “images” as used herein shall mean still images, videoimages, or both.

A. Overview

Most stereoscopic viewing techniques rely on binocular parallax cues togenerate a three-dimensional (3D) image. Binocular parallax refers toseeing a stereo image pair (i.e., two different perspectives) of thesame 3D object or objects. A head mounted display is one of such viewingdevice, in which the user sees two separate stereo images through twoseparated optical paths. Anaglyphic glass, shutter glass, and polarizedglass are widely used to separate the stereo images displayed on asingle screen or printed on the paper.

Autostereoscopic display techniques also rely on parallax depth cues.However, instead of separating the stereo views with glass in front ofthe user's eyes, most of autostereoscopic displays try to control thelight path in display space to generate viewing windows in the user'sspace. In each viewing window, only one monocular image can be observed.The viewing windows further form viewing zones. Since the size of theviewing zone is significantly larger than the size of a human eye, theuser can freely move his/her head within the viewing zone. Most of theexisting autostereoscopic display systems are based on eitherparallel-barrier techniques or lenticular techniques.

1. Parallel-Barrier-Based Display

The fundamental design using a parallel barrier is to place strips toblock light emitted from the display. A black-white mask grid istypically placed in front of the display. Each small white grid acts asa pinhole which maps pixels into the viewing space and allows a user tosee the pixels from certain viewing angle (i.e., creating a viewingwindow), while the black grid blocks the neighbor pixels from thatviewing angle. As a result, in a left viewing window, the user sees oneset of pixels on the display, and in a right viewing window, the usersees the other set of pixels on the display. The left viewing window andthe right viewing window together form one viewing zone. More than oneviewing zone can be formed. Also, by increasing the resolution of thedisplay and associating more pixels to each barrier slits, multipleviewing windows can be created within a single viewing zone.

As previously noted, parallel-barrier-based displays have severaldrawbacks. These drawbacks include: reduced brightness, crosstalkbetween views, diffraction effect caused by a small window, limitedresolution, picket fence effect in the monocular image, image flippingartifact when crossing a viewing zone, and a limited number of viewingwindows.

First, because parallel-barrier-based displays use a light blockstrategy, only a small amount of light emitted from each pixel passesthrough the barrier window. Thus, the brightness of the viewed image isreduced. Attempts to reduce the brightness problem have included placingthe barrier mask behind the display. The light is modulated by thebarrier before reaching the display pixels.

Second, crosstalk between views can be significant. Crosstalk refers tothe overlap of viewing areas, which can result in one eye seeing theimage intended for the other eye. When the crosstalk is significant, thebrain cannot perceive the stereo effect or cannot perceive it correctly.Attempts to minimize the crosstalk artifact involve choosing a barrierpitch for the barrier mask or placing the barrier behind the display.

Third, the use of small apertures in parallel-barrier-based displays cancause diffraction. This problem becomes more acute as the displayresolution increases. As the display resolution increases, the barrieraperture size must be decreased, which causes more severe diffractioneffects. Thus, the aperture size of the barrier is limited by thediffraction limit.

Fourth, parallel-barrier-based displays typically suffer from limitedresolution. For a display with n views, the resolution of the individualview is essentially 1/n of the original display resolution. Because theviews have to divide the resolution of the original display, aparallel-barrier-based display's resolution is limited by the originalresolution of the display, which is also limited by diffraction as wellas the resolution that can be achieved by the display manufacturer.

Fifth, since each view only sees one pixel column out of n associatedwith one barrier window, there are many dark pixels lines in each view.For a two-view case, the dark line is a single pixel width, interlacingin these bright pixels. The dark pixel lines create a “picket fenceeffect” in the monocular image. Attempts to reduce the picket fenceartifact involve placing the barrier lines at an angle with respect tothe pixel column of the display.

Sixth, these displays can suffer from image flipping artifact. Theimaging flipping artifact is caused by the improper alignment of auser's eyes with the viewing windows. In the two-view display systems, auser will see a flipped set of stereo images if the user's left eye isin a right viewing window and the user's right eye is in a left viewingwindow. For a multiple-view display system, such flipping artifactshappen when a user crosses a viewing zone.

Finally, parallel-barrier-based displays typically suffer from having alimited number of viewing windows. In order to generate more viewingwindows, the dark slits have to be wider while the slit windows remainunchanged. It is impossible to increase the number of viewing windowswithout increasing artifacts, such as reduced brightness and picketfence effect.

2. Lenticular-Based Displays

As noted above, one drawback of parallel-barrier-based displays is lowbrightness due to the narrow vertical slits of the barrier. One solutionto this problem is to use lenses to improve the light gathering. Oneform of lens that is used is a lenticular sheet, which contains a set ofcylindrical lenses placed side-by-side. To use a lenticular sheet fordisplaying 3D images, the sheet is vertically aligned with a 2D display.Similar to parallel-barrier displays, if aligning two sets of pixels(e.g., left eye pixels and right eye pixels), two viewing windows can becreated to form one viewing zone. Multiple viewing zones (with L & Rviewing windows) can also be created. If aligning multiple pixels witheach lens, multiple viewing windows can be created in one viewing zone.Since the lenses in the lenticular sheet are in a cylindrical shape,only horizontal parallax is created. In addition to an improvement overparallel-barrier-based displays with respect to light-gathering ability,the lenticular sheet also can offer higher resolution comparing withbarrier slits.

Although lenticular-based displays have better brightness and resolutionpossibilities as compared to parallel-barrier-based displays,lenticular-based displays present their own disadvantages. First, thequality of the display is dependent upon having a high qualitylenticular sheet. However, it is significantly more difficult andcostly, particularly as compared to barrier masks, to manufacture highquality lenticular sheets. Additionally, aligning a lenticular sheetwith a display also requires significant effort. Furthermore,lenticular-based displays also suffer from problems that plagueparallel-barrier-based displays, such as crosstalk between view windows,picket fence problem, limited resolution, image flipping, and limitednumber of viewing windows.

3. Light Diffusion Based Displays

A third type of multiple-view 3D display uses light shaping diffuser(LSD) technology. Examples of devices utilizing light shaping diffusersinclude a light-field display called HoloVizo™ developed by Holografikaof Budapest, Hungary and a 3D light-field display developed by theInstitute for Creative Technologies at the University of SouthernCalifornia. The light shaping diffuser is a one-dimensional lightdiffuser which is used for optical communication device and LCD displaybacklighting. When illuminated by a projector, the light shapingdiffuser has small diffusion in the horizontal direction and largediffusion in the vertical direction

Holografika takes advantage of the one-dimensional diffusion property inits HoloVizo™ display. The display uses a number of projectors thatilluminate a LSD screen. In the horizontal cross-section view, a viewercan only see one very thin slit of images from each projector, assumingthat the screen diffuses light in the vertical direction only. Togenerate one viewing perspective, these thin slits from differentprojectors have to be mosaiced together. Therefore, the display requiresmany projectors to work together. For the HoloVizo™ display system, asmany as 50 projectors are used for the prototype. Assuming a horizontaldiffusion angle of 1 degree, it requires about 60 projectors to generatea 60 degree field-of-view multiple-view display.

The light-field display developed by the Institute for CreativeTechnologies at the University of Southern California consists of ahigh-speed video projector, a spinning mirror covered by a holographicdiffuser, and field-programmable-gate-array circuitry to decodespecially rendered Digital Visual Interface (DVI) video signals. Thehigh-speed video projector and a spinning mirror covered by aholographic diffuser generate a 360 degree view. The light-field displaydeveloped by the Institute for Creative Technologies at the Universityof Southern California has similar properties as the HoloVizo™ display.

Although these displays do not share all of the drawbacks of theparallel-barrier-based and lenticular-based displays, there are someinherent problems with these approaches. For example, there can becrosstalk problem, difficult system calibration, and extra-cost forrendering.

First, for the HoloVizo™ display, there can be crosstalk problems. Thecrosstalk artifact can be introduced by the light diffuser. An idealdiffuser should be a perfect low pass filter (i.e., perfectrectangular). However, the actually material has a Gaussian-likediffusion pattern. As a result, there can be crosstalk between twoneighbor thin slits, which could significantly blur the images orgenerate a zigzag image.

Second, both systems require extremely specialized and complexcomponents and require complex system calibration. For example, sincethe images in the HoloVizo ™ display are mosaiced from image segments ofmany projectors, these projectors must be properly aligned andcalibrated. The light-field display developed by the Institute forCreative Technologies at the University of Southern California alsorequires specialized equipment and specialized set-up.

Finally, there are extra costs for image rendering. For the HoloVizo™display, the rendering costs are caused, at least in part, by itsspecial image mosaic requirement. The images displayed on the projectorsare not the perspective images of a regular 3D movie or the imagesrendered by the standard OpenGL software. Thus, extra steps have to betaken to generate proper images for each projector. And, for thelight-field display developed by the Institute for Creative Technologiesat the University of Southern California, the system requires speciallyrendered DVI video signals.

B. Embodiments of Autostereoscopic Display

Embodiments of the present invention include using light shape diffusionwith retro-reflection. Such configurations have several benefits overprior autostereoscopic displays. First, such systems can use fullresolution of the projectors and can display bright images. Systems ofthe present invention generate each view image with only one projectorand do not require mosaicing the views from multiple projectors when theuser views images at the designated viewing location. Additionally, theimages do not require specially rendered video signals. As a result, thespecial post-rendering processes mentioned above are not necessary.Compared with parallel-barrier-based and lenticular-based displays, thepresent systems do not suffer from the same resolution limits, aretypically much brighter, and are theoretically able to create a largenumber of viewing windows. Additional benefits shall be apparent to oneskilled in the art.

C. Retro-reflective Vertical Light Diffusion Screen (RRVLD)

In embodiments, an autostereoscopic display of the present inventioncomprises two layers. The first layer comprises a one-dimensional (1D)light diffusion material that has a small diffusion angle in onedirection and a large diffusion angle in the other direction. FIG. 1depicts an example of a light diffusing material according toembodiments of the invention.

As showing in FIG. 1, an incident light ray 105 that passes through thelight diffusing material 110 is diffused by a small angle 115 in thehorizontal direction but by a large angle 120 is the vertical direction.For 3D display applications, a small diffusion in the horizontaldirection is preferred, while in the vertical direction a largediffusion is preferred. Therefore, this type of diffusion screen can bereferred to as a vertical light diffusion screen.

The second layer of the screen is a retro-reflective material, whichreflects a light ray back in the incident direction. FIG. 2 depicts anexample of a retro-reflective material and the interaction with lightrays. An incident light ray 210 or 220 strikes the retro-reflectivematerial 205 and is reflected. The reflected light ray is reflected backat the same, or nearly the same, angle as the incident light ray. Thus,the incident light ray 210 has a retro-reflective ray 215 that isreflected back to along the direction of the incident ray 210. And, theincident light ray 220 has a retro-reflective ray 225 that is reflectedback to along the direction of the incident ray 220.

FIG. 3 depicts a retro-reflective vertical light diffusion screen 300according to various embodiments of the invention. The screen 305illustrated in FIG. 3 is formed of a light diffusion material 310combined with a retro-reflective material 315. In embodiments, aone-dimensional light diffusion material, such as Light ShapingDiffusers (LSD®) produced by Luminit LLC of Torrence, Calif., may beused. A light shaping diffusion material may have diffusion angles of60°×1°, although one skilled in the art shall recognize that otherdiffusion angles may be used. In embodiments of the 3D display system,the light shaping diffusion material is oriented with the 60° diffusionangle in the vertical direction and with the 1° diffusion angle in thehorizontal direction. In embodiments, a retro-reflective material, suchas 3M™ Scotchlite™ Reflective Material, produced by 3M Corporation ofSt. Paul, Minn. or the photoelectric control products, such as its P66and AC1000 with metalized back produced by Reflexite Americas of NewBritain, Conn., may be used.

As depicted in FIG. 3, light 320 directed toward the retro-reflectivevertical light diffusion screen 305 passes through the diffusionmaterial and is retro-reflected back to along its incident direction 325(or substantially along the incident direction). The retro-reflectedlight is then diffused by the light diffusion material 310. The lightdiffusion material 310 is configured to diffuse the retro-reflectedlight a small amount in the horizontal direction 330 and a large amountinto vertical direction 335. Thus, the resulting diffused light is in afan shape after it passes through the diffusion material.

D. Embodiments of Display Systems 1. General Display System Embodiments

FIG. 4 depicts a display system 400 according to various embodiments ofthe present invention. Shown in FIG. 4 is a retro-reflective verticallight diffusion screen 405 and a projector 410. The retro-reflectivevertical light diffusion screen 405 is used as a display screen. Thelight rays 415 emitted from the projector are retro-reflected back tothe projector 410 and create a viewing window 425 which overlaps withthe projector. The screen 405 is configured such that the reflectedlight is diffused with a large diffusion angle in the vertical directionand with a small diffusion angle in the horizontal direction. Due to thevertical diffusion effect, the viewing window is a vertical slitcentered with the aperture of the projection lens. The width of the slit425 is a function of the horizontal diffusion angle of the screen, thedistance from the projector, and the aperture size of the projectionlens. The following equation sets forth the calculation for the width ofthe vertical slit:

${W = {D_{a} + {2 \cdot Z_{p} \cdot {\tan \left( \frac{\varpi}{2} \right)}}}},$

where

W is the width of the slit;

D_(a) is the aperture size of the projection lens;

Z_(p) is the distance from the projector to the screen; and

ω is the horizontal diffusion angle of the screen.

It shall be noted that an advantage of having a large vertical diffusionangle is that the viewing window is extended. Without an extendedviewing window, the viewing window would coincide with the projectorlens, thereby making it not possible for an individual to view thereflected image. By extending the viewing window in a verticaldirection, a user can view the image in the viewing window either aboveor below the projector 410.

FIG. 5 depicts a 3D display system 500 according to various embodimentsof the present invention. Shown in FIG. 5 is a retro-reflective verticallight diffusion screen 505 and a set of projectors 510A-F. It should benoted that although FIG. 5 depicts six projectors, additional or fewerprojectors could be used. The retro-reflective vertical light diffusionscreen 505 is used as the display screen in a similar manner asdescribed with reference to FIG. 4. Namely, the light rays 515 emittedfrom a projector 510 x are reflected back to the projector 510 x andcreate a viewing window 525 x overlapped with the projector. Forexample, the light from projector 510A is reflected and diffused by thescreen 505 to form viewing window 525A. This result is same for eachprojector in the display system 500, wherein each projector 510A-Fgenerates a corresponding viewing window 525A-F, respectively. Thus, byadding more projectors, more such viewing windows are created.

The display system depicted in FIG. 5 generated six distinct viewingwindows. Each viewing window displays an image from a correspondingprojector. By displaying a set of images captured from multipleperspectives on the screen through the projectors, a user can see 3Dthrough these viewing slits or windows. For example, if a user views oneimage in one viewing window with one eye and views another perspectiveimage in another viewing window with her other eye, then the user willperceive a 3D image. In embodiments, the width of a slot can besufficiently small that a user does not perceive a monocular image byviewing the same image in the same viewing window with both eyes.

One skilled in the art shall recognize that there are several advantagesto a display system of the kind depicted in FIG. 5. First, the imagesare bright. Due to the one-dimensional light diffusion, a user will seean image that is much brighter than the image on a regular diffusionscreen or using other stereoscopic methods like parallel-barrier-baseddisplays.

Second, the display screen can be configured into different shapes. Dueto the retro-reflective property of the material, the screen shape couldtake arbitrary forms, such as regular planar, cylindrical shape,spherical shape, or almost any irregular shape. These shape variationsdo not affect the refocusing property of the retro-reflective screen.

Third, the display system is easily scalable. For example, more viewingwindows can be generated by simply adding more projectors.

Fourth, the display system does not have the resolution limitations ofprior solutions. Even though all the images are projected on the samescreen, each image is only seen in the designated viewing window;therefore, the resolution can be as high as the resolution of theprojector.

Fifth, the display system does not suffer from the picket fence effect.Because the user perceives one full resolution image from a singleprojector at each viewing window, there is no picket fence effect in theimage.

Sixth, the display system does not suffer from an image flipping effect.The flipping effect occurs when a user moves his head across the viewingzones and perceives a right image in his left eye and a left image inhis right eye. The display system does not have repeated viewing zoneswith specific stereo pair images and therefore does not have imageflipping problems. Rather, each viewing window displays a perspectiveview image and any pair of images forms a 3D view. For example, inembodiments, the viewing windows may have a progression of perspectiveview images, wherein any two images form a 3D view.

Finally, the display system can potentially have an infinity number ofviewing windows. Although theoretically the display system can generatean infinity number of viewing windows, the number of viewing windowsthat can be generated depends upon the horizontal diffusion angle of thediffusion material, the distance from the projector to the screen andthe size of the projector.

2. Compact Design Embodiments

FIG. 6 depicts an alternative embodiment of a display system accordingto various embodiments of the invention. Illustrated in FIG. 6 is a morecompact design for a display system 600. The depicted display system 600comprises a retro-reflective vertical light diffusion screen 605 and aprojector 610. Instead of having the projector 610 project an image 615directly on the screen 605, the projector 610 projects an image onto abeamsplitter 620. The light reflects off the beamsplitter 620 or issplit by the beamsplitter 620 onto the retro-reflective vertical lightdiffusion screen 605. The retro-reflected light, or at least a portionof the retro-reflected light, passes through the beamsplitter 620 tocreate a view window 630 where a virtual position of the projector 635is located. It shall be noted that using a beamsplitter to fold thelight path has at least two benefits. First, the view window 630 is notoccluded by the projector since the view window is moved to a virtuallocation 635 of the projector. And second, the display system has acompact design. In embodiments, a first surface mirror could be insertedin the optical path to further fold the light path, if necessary. Forexample, a mirror can be used to bend the light path and allowing theprojector to be moved closer to the screen.

3. Dual Screen Display System Embodiments

Although the embodiment depicted in FIG. 6 creates a more compactdesign, the resulting image in the viewing window may be perceived asbeing less bright due to the energy loss as part of the beamsplitting.FIG. 7 illustrates an alternative embodiment of a display system withtwo retro-reflective vertical light diffusion screens according tovarious embodiments of the invention to address this light-loss issue.

FIG. 7 depicts a similar configuration 700 as the display system 600shown in FIG. 6. The depicted display system 700 comprises aretro-reflective vertical light diffusion screen 705A and a projector710 in the same or similar configuration as the system 600 illustratedin FIG. 6. As noted above, one issue of the display system 600 in FIG. 6is that approximately half the energy is lost when the light passesthrough the beamsplitter each time. Thus, approximately 25% of the lightactually reaches the user viewing window 630. One solution to thisproblem is to place a secondary retro-reflective vertical lightdiffusion screen 705B at a position optically mirror-conjugated with theoriginal screen 705B. This causes the light reflected from the secondaryretro-reflective vertical light diffusion screen 705B to add with thelight reflected from the primary retro-reflective vertical lightdiffusion screen 705A that forms the viewing window 730. Thus, using thedisplay system 700 depicted in FIG. 7 can increase the image brightnessby a factor of 2 over the display system 600 depicted in FIG. 6.

4. Polarization Managed Display System Embodiments

FIG. 8 illustrates yet another embodiment of a display system with aretro-reflective vertical light diffusion screen according to variousembodiments of the invention. The display system 800 illustrated in FIG.8 is not only an alternative display system but also provides anothersolution to the energy loss issue noted with respect the system 600illustrated in FIG. 6.

FIG. 8 depicts a configuration 800 that is similar to the configurationof the display system 600 shown in FIG. 6. The depicted display system800 comprises a retro-reflective vertical light diffusion screen 805 anda projector 810 in the same or similar configuration as the system 600illustrated in FIG. 6. However, as illustrated in FIG. 8, apolarization-sensitive beamsplitter 820 is used. Such a beamsplitter hasnear 100% reflection rate for polarized light when the lightpolarization direction matches with the polarization direction of thebeamsplitter and near 100% transitivity if the light polarizationdirection is orthogonal to the polarization direction of thebeamsplitter. Thus, after the light 815 is reflected toward the screen805, a quarter-wave plate 840 is used to rotate the light 45°. When thelight is reflected from the screen 805, it is rotated another 45° whenit again passes through quarter-wave plate 840. The polarization of theresulting light is orthogonal to the polarization of the light 815 andwill pass through the polarization-sensitive beamsplitter 820. Thus,near 100% of the light reaches the user space in the viewing window 830.This approach can increase the image brightness in the viewing window830 by a factor of 4 over the configuration depicted in FIG. 6.

It shall be noted that the configurations shown in FIGS. 6-8 weredepicted with a single projector to simply the explanation. One skilledin the art shall recognize that additional projectors can be added toany of the disclosed systems.

5. Additional Layer Embodiments a) Transparent Layer Embodiments

When an image is projected onto a retro-reflective surface, the vastmajority of the light is retro-reflected back to the image source.However, because retro-reflectors are not perfect, some light isdiffused or reflected in other directions. This diffused or errantlyreflected light can create unwanted images, known as ghost images.

An anti-reflection coating on the reflection surface would reduce theghost images from the diffusion. However, this solution can be veryexpensive. As an alternative solution, presented herein is a transparentmedium gap between the diffusor and the retro-reflective material. Thetransparent space allows the ghost image to blur on the retro-reflectivematerial, while keeping the image on the diffuser sharp because of thefocusing ability of the retro-reflective material. Furthermore, thefront diffusor layer diffuses the already blurred ghost image, whichfurther dims the ghost image. As a result, a user will see a darker andblurred ghost image, if at all.

As discussed above, when the light diffusion material is placed in frontof the retro-reflective material, light is reflected back along theincident direction by the retro-reflective layer and is diffused into afan shape by the light diffusing material. The resulting reflected lightrays create a viewing window. Each viewing window displays an image of aprojector. Accordingly, multi-projectors combined with theretro-reflective light diffusion screen can produce multiple viewingwindows. If those windows display images from different perspectives,the multi-projector and screen system forms a three-dimensional displaysystem. That is, by using the projectors to display a set of imagescaptured from multiple perspectives, a user can see a three-dimensionalimage via the viewing windows that are formed. However, if there isimperfection in the screen, ghost images may be formed.

In embodiments of the light diffuser and retro-reflective screen systemas discussed above, an image is focused on the diffuser and theretro-reflective material. Both the retro-reflected image on thediffuser and the ghost image on the retro-reflective material are sharp.The diffused or misdirected light of the ghost image is in focus. If theghost image is sufficiently bright, it can be seen in viewing windowsand would interfere with a user's ability to perceive the proper imagefor that view window. When the ghost image is significant, the user maynot be able to perceive a stereo view.

In embodiments, to reduce the effects of ghost images, a third layer isintroduced between the retro-reflective material and the light shapingdiffuser. This layer allows the diffused light to further diffuse, whichcauses it to be dimmed and significantly blurred while still allowingthe retro-reflected image to remain sharp.

FIG. 9 illustrates an embodiment of a three-layer retro-reflective lightdiffusion screen 905 according to various embodiments of the invention.The screen depicted in FIG. 9 comprises a light diffuser 910 and aretro-reflector 915, which are separated by a transparent medium 920. Inembodiments, the width of the transparent gap was between 10-30millimeters, although other widths values may be used. The transparentmedium may be, by way of example and not limitation, glass, plastic, avacuum or nearly vacuum space, or transparent (or substantiallytransparent) gas or gases.

In a projector system, the projector is focused on the first layer—thediffuser 910. Therefore, the image on the diffuser is sharp. However,the image on the retro-reflective material 915 is significantly blurredbecause space exists due to the transparent medium 920 for the image todiffuse before reaching the retro-reflector 915. As illustrated in FIG.9, an image point 930 on the diffuser 910 is a blurred area 935 on theretro-reflector 915. Therefore, the image on the retro-reflector isblurred.

Although most of the light will be properly retro-reflected, some lightrays (e.g., 940-x) are imperfectly reflected or diffused and travel invarious directions. These light rays will be further diffused whenpassing through the diffuser 910. Therefore, the ghost images will beadditionally blurred and darkened after passing through the diffuser910. For example, light ray 940-1 travels through diffuser 910 and isfurther diffused by the diffuser 910 to create even more dispersed, andtherefore dimmer, light rays 945.

FIG. 10 illustrates the triple-layer retro-reflective light diffusionscreen of FIG. 9 for the retro-reflective light according to variousembodiments of the invention. Most of the light incident on theretro-reflector 915 will be retro-reflected back 1005. Thus, even thoughthe image on the retro-reflector 915 is blurred, the retro-reflectedlight rays are focused 930 on the light diffuser 910 due to theretro-reflective property of the retro-reflector 915. Therefore, theretro-reflective image remains sharp despite the introduction of the gapformed by the transparent medium 920.

Since the image is focused on the light diffuser 910, after the image isproperly diffused by the diffuser 910 and forms a view window 1010 bybeing diffused vertically but only diffused slightly in the horizontaldirection, in the view window 1010, a user will see a sharp image. And,the user will see less, if any, of the greatly diffused ghost images.

It shall be noted that the triple layer screen embodiments may also beutilized in the embodiments discussed above with respect to the duallayer screen.

b) Lenticular Layer Embodiments

A lenticular sheet contains many cylindrical lens (one-dimensional lens)arranged side-by-side. Since the lenses are one dimensional, alenticular sheet has focusing ability in only one direction. Lenticularsheets have been used in both transparent-type and reflection-typethree-dimensional displays. For example, a lenticular reflection screen(LRS) contains two layers: a lenticular sheet and a regular diffusionsurface. In the vertical direction, the light is diffused in all thedirections, and in the horizontal direction, the light is first diffusedand then refocused back to the projector by the one-dimensional lenses.

Although lenticular reflection screens have been used inthree-dimensional displays, lenticular reflection screens havesignificant limitations. When projecting images on a lenticularreflection screen, a set of projector form not only a main viewing zonebut also side viewing zones, similar to a transparent-type configurationprojection system. If additional projectors are placed outside of themain viewing zone in a side viewing zone, crosstalk between theprojected images can occur, which limits the field of view of thelenticular sheet system. FIG. 11 illustrates an example such of alenticular reflection screen configuration.

FIG. 11 illustrates the formation of viewing zones from a lenticularreflection screen system 1100 and the crosstalk that can exist in suchsystem. The lenticular reflection screen system in FIG. 11 includes atypical lenticular reflection screen 1105 and a set of projector 1135.The lenticular reflection screen 1105 is a lenticular sheet 1110 and aregular diffusion surface 1115. The lenticular sheet 1110 is formed froma plurality of parallel, one-dimensional lenses 1110-x. The set ofprojectors 1135 project images, such as a multi-view image set, onto thescreen 1105. Light from the projector set 1135 form a corresponding mainviewing zone 1120, containing multiple viewing windows 1140. The numberof viewing windows 1140 formed within the main viewing zone 1120 is thesame as the number of the projectors placed within the main viewing zone1120. The number of projectors that can be placed within the mainviewing zone is related to the width of the viewing window, the distancefrom the projectors to the screen, and the field of view of thelenticular lens. In addition to the main viewing zone 1120, several sideviewing zones with corresponding sets of viewing windows (e.g., 1145Land 1145R) are also formed as a result of the large diffusion angle ofusing a regular diffuser 1115 in the lenticular reflection screen 1105.

As illustrated in FIG. 11, the light from the projector 1130 is imagedat point 1155 through lens 1110-1. The light is returned and forms aview window 1150 in the set of viewing windows 1140 in the main viewingzone 1120. Due to large diffusion angle of the regular diffuser surface1115, the diffused light at point 1155 reaches not only the lens 1110-1,but also neighboring lenses (e.g., 1110-2, 1110-3, 1110-4, 1110-5, andso on). As a result, in addition to the viewing windows 1140 formed inmain viewing zone 1120, multiple viewing windows (e.g., 1155L and 1155R)are formed in side viewing zones (e.g., 1125L and 1125R,respectively)—one in each side viewing zones. To simply the figure, onlytwo viewing windows (1155L and 1155R) in two side viewing zones (1125Land 1125R) are showed.

When multiple projectors 1135 are used to form multiple viewing windows1140 in the main viewing zone 1120, in each side viewing zone acorresponding set of the viewing windows (e.g., a set of viewing windows1145L in side viewing zone 1125L and a set of viewing windows 1145R inside viewing zone 1125R) are also formed.

If another projector 1160 is placed inside a side viewing zone 1125L toproject images onto the screen 1105, light from the projector 1160 formsa corresponding main viewing window in side viewing zone 1125L and sideviewing windows in main viewing zone 1120 and side viewing zone 1125R,and these viewing windows could overlap with the viewing windows formedby the set of projectors 1135. For example, the light from the projector1160 in the side viewing zone 1125L may interfere with light from theprojector 1130 in the set of projectors 1135 in the main viewing zone1120. Accordingly, crosstalk between the reflected images exists. If thecrosstalk is significant, it can impede the ability of a user toperceive stereo images.

Because a projector or set of projectors cannot placed outside of themain viewing zone of a main projector set without creating crosstalkissues, a typical LRS-based system can be very limited because its fieldof view for the main view area is limited. FIG. 12 illustrates anembodiment of a retro-reflective light diffusion screen with alenticular layer according to various embodiments of the invention thatextends the main viewing zone.

Depicted in FIG. 12 is a retro-reflective light diffusion screen 1205,which comprises a lenticular layer 1220, a light diffuser 1210, and aretro-reflector 1215. In embodiments, a screen 1205 may be formed bycombining a lenticular layer 1220 with the dual layer retro-reflectivelight diffusing screen described previously. The lenticular layer 1220is configured such that the light diffuser is at the focus plane, f, ofthe cylindrical lenses of the lenticular layer. Incident light thattraveled through the lenticular lens and the light diffuser is reflectedback in the direction of the incident light by the retro-reflectivematerial 1215. The light diffuser 1210 diffuses the retro-reflectedlight in a large angle in the vertical direction but only by a smallangle in the horizontal direction. A tighter horizontal diffusion angleallows the light travel back to only one lens, therefore, only forms alarger main field of view and no side viewing zone. As a result, themain field of view 1230 is larger than a typical LRS's main viewing zone1235.

Such a screen 1205 as the one depicted in FIG. 12 has severaladvantages. First, the screen 1205 eliminates the side viewing zones,and therefore, reduces crosstalk. Second, the screen 1205 has anincreased overall field of view and extended main viewing zone. As shownin FIG. 12, the three component screen 1205 has a larger main viewingzone 1230 as compared to the main viewing zone 1235 of a regularlenticular screen, such as the screen 1105 in FIG. 11. And finally, thescreen 1205 can produce an increased brightness because of the addedfocus from the lenticular layer.

In addition to the reducing the crosstalk issue related to side viewingzones, the retro-reflective light diffusion screen with the lenticularlayer addresses another crosstalk problem due to the diffusion profileof the diffuser. FIG. 13 depicts the light distribution of a view windowfrom an embodiment of a retro-reflective light diffusion screenaccording to various embodiments of the invention. As depicted in theFIG. 13, the light distribution 1305 of the diffused light follows aGaussian distribution. As best seen in the vertically direction, thelight is brightest at the center and fades in brightness toward the topand bottom. The diffused light 1305 also has a Gaussian distribution inthe horizontal direction as well. FIG. 14 depicts examples of across-section of the diffused light 1305.

FIG. 14 depicts the cross-section of two adjacent view windows 1405-1and 1405-2 from an embodiment of a retro-reflective light diffusionscreen according to various embodiments of the invention. As depicted inFIG. 14, the two adjacent view windows 1405-1 and 1405-2 are formed fromtwo diffused light regions 1410-1 and 1410-2 from a retro-reflectivelight diffusion screen. The light regions 1410-1 and 1410-2 follow aGaussian distribution, and because the light passes through the lightdiffuser twice, the diffusion angle is approximately the square root of2 times larger than the diffusion angle of the light shaping diffuser.

Because the light follows a Gaussian distribution, there is no welldefined energy cutoff boundary. In embodiments, the view window may bedefined as the region at which the intensity of the light is above athreshold value or percentage, such as, by way of example and notlimitation, 50% of the maximum. Because of the distribution, some energymay leak to the neighbor viewing windows as depicted in FIG. 14 (region1430). By adding a lenticular lens layer to a retro-reflective lightdiffusion screen, the lenticular layer focuses the diffused light andcreates a more tightly distributed light region. The more tightlydistributed light profiles create viewing windows with more well definedboundaries and reduces or eliminates crosstalk due to energy leakage.For a retro-reflective light diffusion screen with a very smallhorizontal diffusion angle, a lenticular layer may not providesignificant advantage. However, if the view windows formed by the screenexhibit significant crosstalk, the addition of a lenticular layer canhelp minimize the crosstalk.

It shall be noted that the retro-reflective light diffusion screen witha lenticular layer may also be utilized in the embodiments discussedabove with respect to the dual layer screen.

c) Lenticular Layer and Transparent Layer Embodiments

FIG. 15 illustrates yet another embodiment of a retro-reflectivevertical light diffusion screen according to various embodiments of theinvention. Depicted in FIG. 15 is a retro-reflective light diffusionscreen 1505, which comprises a lenticular layer 1520, a transparentmedium layer 1525, a light diffuser 1510, and a retro-reflector 1515.Such a configuration can have the benefits of reducing ghost images andreduce crosstalk. It shall be noted that such a screen may be also beutilized in the embodiments discussed above with respect to the duallayer screen.

E. Display System Embodiments

FIG. 16 illustrates a multi-projector display system with at least oneretro-reflective vertical light diffusion screen according to variousembodiments of the invention. The system comprises a retro-reflectivelight diffusion screen 1605 and a plurality of projectors 1610. In thedepicted system 1600, the projectors 1610A-x may be under the control ofa computing system 1620. In embodiments, the computing system contains,or alternatively is communicatively connected to, a datastore 1630 thatstores a set of perspective images. The computing system 1620coordinates the displaying of perspective views on the screen 1605 viathe projectors 1610A-x to generate an autostereoscopic display.

One skilled in the art shall recognize that system depicted in FIG. 16may be configured in a number of different ways, include withoutlimitation, using one or more of the configurations illustrated in FIGS.5-10, 12, and 15. No particular configuration is critical to the presentinvention.

It shall be noted that the present invention may be implemented using aninstruction-execution/computing device or system capable of processingdata, including without limitation, a general-purpose computer and aspecific computer, such as one intended for data or image processing.The present invention may also be implemented with other computingdevices and systems. Furthermore, aspects of the present invention maybe implemented in a wide variety of ways including software, hardware,firmware, or combinations thereof. For example, the functions topractice various aspects of the present invention may be performed bycomponents that are implemented in a wide variety of ways includingdiscrete logic components, one or more application specific integratedcircuits (ASICs), and/or program-controlled processors. It shall benoted that the manner in which these items are implemented is notcritical to the present invention.

FIG. 17 depicts a functional block diagram of an embodiment of aninstruction-execution/computing device 1700 that may be implemented withembodiments of the present invention. As illustrated in FIG. 17, aprocessor 1702 executes software instructions and interacts with othersystem components. In an embodiment, processor 1702 may be a generalpurpose processor such as (by way of example and not limitation) an AMDprocessor, an INTEL processor, a SUN MICROSYSTEMS processor, or aPOWERPC compatible-CPU, or the processor may be an application specificprocessor or processors. A storage device 1704, coupled to processor1702, provides long-term storage of data and software programs. Storagedevice 1704 may be a hard disk drive and/or another device capable ofstoring data, such as a magnetic or optical media (e.g., diskettes,tapes, compact disk, DVD, and the like) drive or a solid-state memorydevice. Storage device 1704 may hold programs, instructions, and/or datafor use with processor 1702. In an embodiment, programs or instructionsstored on or loaded from storage device 1704 may be loaded into memory1706 and executed by processor 1702. In an embodiment, storage device1704 holds programs or instructions for implementing an operating systemon processor 1702. In embodiments, possible operating systems include,but are not limited to, UNIX, AIX, LINUX, Microsoft Windows, and theApple MAC OS. In embodiments, the operating system executes on, andcontrols the operation of, the computing system 1700. In embodiments,the datastore 1630 may be storage 1704.

An addressable memory 1706, coupled to processor 1702, may be used tostore data and software instructions to be executed by processor 1702.Memory 1706 may be, for example, firmware, read only memory (ROM), flashmemory, non-volatile random access memory (NVRAM), random access memory(RAM), or any combination thereof. In one embodiment, memory 1706 storesa number of software objects, otherwise known as services, utilities,components, or modules. One skilled in the art will also recognize thatstorage 1704 and memory 1706 may be the same items and function in bothcapacities. In an embodiment, one or more of the software components ormodules may be stored in memory 1704, 1706 and executed by processor1702.

In an embodiment, computing system 1700 provides the ability tocommunicate with other devices, other networks, or both. Computingsystem 1700 may include one or more network interfaces or adapters 1712,1714 to communicatively couple computing system 1700 to other networksand devices. For example, computing system 1700 may include a networkinterface 1712, a communications port 1714, or both, each of which arecommunicatively coupled to processor 1702, and which may be used tocouple computing system 1700 to other computer systems, networks, anddevices.

In an embodiment, computing system 1700 may include one or more outputdevices 1708, coupled to processor 1702, to facilitate displayinggraphics and text. Output devices 1708 may include, but are not limitedto, a projector, a display, LCD screen, CRT monitor, printer, touchscreen, or other device for displaying information. Computing system1700 may also include a graphics adapter (not shown) to assist indisplaying information or images on output device 1708.

One or more input devices 1710, coupled to processor 1702, may be usedto facilitate user input. Input device 1710 may include, but are notlimited to, a pointing device, such as a mouse, trackball, or touchpad,and may also include a keyboard or keypad to input data or instructionsinto computing system 1700.

In an embodiment, computing system 1700 may receive input, whetherthrough communications port 1714, network interface 1712, stored data inmemory 1704/1706, or through an input device 1710, from a scanner,copier, facsimile machine, or other computing device.

One skilled in the art will recognize no computing system is critical tothe practice of the present invention. One skilled in the art will alsorecognize that a number of the elements described above may bephysically and/or functionally separated into sub-modules or combinedtogether.

It shall be noted that embodiments of the present invention may furtherrelate to computer products with a computer-readable medium that havecomputer code thereon for performing various computer-implementedoperations. The media and computer code may be those specially designedand constructed for the purposes of the present invention, or they maybe of the kind known or available to those having skill in the relevantarts. Examples of computer-readable media include, but are not limitedto: magnetic media such as hard disks, floppy disks, and magnetic tape;optical media such as CD-ROMs and holographic devices; magneto-opticalmedia; and hardware devices that are specially configured to store or tostore and execute program code, such as application specific integratedcircuits (ASICs), programmable logic devices (PLDs), flash memorydevices, and ROM and RAM devices. Examples of computer code includemachine code, such as produced by a compiler, and files containinghigher level code that are executed by a computer using an interpreter.Embodiments of the present invention may be implemented in whole or inpart as machine-executable instructions that may be in program modulesthat are executed by a computer. Examples of program modules includelibraries, programs, routines, objects, components, and data structures.In distributed computing environments, program modules may be physicallylocated in settings that are local, remote, or both.

While the invention is susceptible to various modifications andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formsdisclosed, but to the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the scope ofthe appended claims.

1. A screen system comprising: a screen comprising: a two-dimensionalretro-reflective surface configured to retro-reflect an image thatpassed through a diffusion layer to form a reflected image; thediffusion layer that receives the reflected image from thetwo-dimensional retro-reflective surface and diffuses the reflectedimage to form a viewing window corresponding to the image by diffusingthe reflected image by a large diffusion angle in a first direction anddiffusing the reflected image by a small diffusion angle in a seconddirection; and a transparent medium, positioned between thetwo-dimensional retro-reflective surface and the diffusion layer, thatallows the image to be out of focus at the two-dimensionalretro-reflective surface and wherein at least a portion of theout-of-focus image that was not retro-reflected by the two-dimensionalretro-reflective surface is diffused by the diffusion layer.
 2. Thescreen system of claim 1 further comprising: a plurality of projectors,each projector having a unique position and configured to project aunique image onto the screen to form a viewing window corresponding tothe projected image.
 3. The screen system of claim 2 wherein: the screensystem forms a plurality of viewing windows corresponding to a pluralityof images projected by the plurality of projectors, the plurality ofviewing windows being positioned such that a user can view athree-dimensional image by viewing a first unique perspective image witha first eye at a first viewing window selected from the plurality ofviewing windows and viewing a second unique perspective image with asecond eye at a second viewing window from the plurality of viewingwindows.
 4. The screen system of claim 2 further comprising: abeamsplitter positioned in an optical path between at least one of theplurality of projectors and the screen to direct a projected image tothe screen and to direct the projected image reflected from the screento a location to form a viewing window that is spatially separate fromthe at least one of the plurality of projectors.
 5. The screen system ofclaim 4 wherein the screen is a first screen and the system furthercomprises: a second screen comprising: a two-dimensionalretro-reflective surface configured to retro-reflect an image thatpassed through a diffusion layer to form a reflected image; thediffusion layer that receives the reflected image from thetwo-dimensional retro-reflective surface and diffuses the reflectedimage to form a viewing window corresponding to the image by diffusingthe reflected image by a large diffusion angle in a first direction anddiffusing the reflected image by a small diffusion angle in a seconddirection; and a transparent medium, positioned between thetwo-dimensional retro-reflective surface and the diffusion layer, thatallows the image to be out of focus at the two-dimensionalretro-reflective surface and wherein at least a portion of theout-of-focus image that was not retro-reflected by the two-dimensionalretro-reflective surface is diffused by the diffusion layer; and thesecond screen is configured to increase the brightness of the image at aviewing window that is coincide with a viewing window formed from thefirst screen.
 6. The screen system of claim 5 wherein the second screenis positioned at an optically mirror-conjugated position relative to thefirst screen.
 7. The screen system of claim 4 wherein the beamsplitteris a polarization-sensitive beamsplitter and the system furthercomprises a quarter-wave plate positioned in an optical path between thescreen and the beamsplitter.
 8. The screen system of claim 2 furthercomprising: a computing device communicatively coupled to the pluralityof projectors to coordinate projection of images.
 9. A screen systemcomprising: a screen comprising: a lenticular layer that receives animage and focuses the image onto a light diffuser layer and thatreceives a diffused reflected image from the light diffuser layer andfocuses the diffused reflected image to form a viewing window; the lightdiffuser layer, position at the focal plane of the lenticular layer,that receives the image from the lenticular layer and that receives areflected image from the two-dimensional retro-reflective surface anddiffuses the reflected image to form the diffused reflected image; andthe two-dimensional retro-reflective surface that receives the imagefrom the light diffuser layer and retro-reflects at least a portion ofthe image back to the light diffuser layer to form the reflected image.10. The screen system of claim 9 further comprising: a plurality ofprojectors, each projector having a unique position and configured toproject a unique image onto the screen to form a viewing windowcorresponding to the projected image.
 11. The screen system of claim 10wherein: the screen system forms a plurality of viewing windowscorresponding to a plurality of images projected by the plurality ofprojectors, the plurality of viewing windows being positioned such thata user can view a three-dimensional image by viewing a first uniqueperspective image with a first eye at a first viewing window selectedfrom the plurality of viewing windows and viewing a second uniqueperspective image with a second eye at a second viewing window from theplurality of viewing windows.
 12. The screen system of claim 10 furthercomprising: a beamsplitter positioned in an optical path between atleast one of the plurality of projectors and the screen to direct aprojected image to the screen and to direct the projected imagereflected from the screen to a location to form a viewing window that isspatially separate from the at least one of the plurality of projectors.13. The screen system of claim 12 wherein the screen is a first screenand the system further comprises: a second screen comprising: alenticular layer that receives an image and focuses the image onto alight diffuser layer and that receives a diffused reflected image fromthe light diffuser layer and focuses the diffused reflected image toform a viewing window; the light diffuser layer, position at the focalplane of the lenticular layer, that receives the image from thelenticular layer and that receives a reflected image from thetwo-dimensional retro-reflective surface and diffuses the reflectedimage to form the diffused reflected image; and the two-dimensionalretro-reflective surface that receives the image from the light diffuserlayer and retro-reflects at least a portion of the image back to thelight diffuser layer to form the reflected image; and the second screenis configured to increase the brightness of the image at a viewingwindow that is coincide with a viewing window formed from the firstscreen.
 14. The screen system of claim 13 wherein the second screen ispositioned at an optically mirror-conjugated position relative to thefirst screen.
 15. The screen system of claim 12 wherein the beamsplitteris a polarization-sensitive beamsplitter and the system furthercomprises a quarter-wave plate positioned in an optical path between thescreen and the beamsplitter.
 16. The screen system of claim 10 furthercomprising: a computing device communicatively coupled to the pluralityof projectors to coordinate projection of images.
 17. The screen systemof claim 9 further comprising: a transparent medium, positioned betweenthe two-dimensional retro-reflective surface and the light diffuserlayer, that allows the image to be out of focus at the two-dimensionalretro-reflective surface and wherein at least a portion of theout-of-focus image that was not retro-reflected by the two-dimensionalretro-reflective surface is diffused by the light diffuser layer.
 18. Amethod for making a three-dimensional display comprising: positioning ascreen to receive projected images from a plurality of projectors, thescreen comprising: a two-dimensional retro-reflective surface; adiffusion layer, configured with a first diffusion angle in a firstdirection and a second diffusion angle in a second direction, the firstdiffusion angle being substantially larger than the second diffusionangle, the diffusion layer configured to receive an image reflected fromthe two-dimensional retro-reflective surface and to diffuse the image toform a viewing window corresponding to the image; and at least oneadditional layer comprising either a transparent medium positionedbetween the a two-dimensional retro-reflective surface and the diffusionlayer or a lenticular layer positioned such that the diffusion layer isbetween the lenticular layer and the two-dimensional retro-reflectivesurface and is also positioned so that the diffusion layer is at a focalplane of the lenticular layer; configuring the plurality of projectorsto project onto the screen, each projector having a unique position andconfigured to project an image with a unique perspective view onto thescreen to form a viewing window corresponding to the projected image;wherein a plurality of viewing windows are formed corresponding to theplurality of images projected by the plurality of projectors, theplurality of viewing windows being positioned such that a user can viewa three-dimensional image by viewing a first perspective image with afirst eye at a first viewing window selected from the plurality ofviewing windows and by viewing a second perspective image with a secondeye at a second viewing window from the plurality of viewing windows.19. The method of claim 18 further comprising: positioning abeamsplitter in an optical path between at least one of the plurality ofprojectors and the screen to direct a projected image to the screen andto direct the projected image reflected from the screen to a location toform a viewing window that is spatially separate from the at least oneof the plurality of projectors.
 20. The method of claim 19 wherein thebeamsplitter is a polarization-sensitive beamsplitter and the methodfurther comprises: positioning a quarter-wave plate in an optical pathbetween the screen and the beamsplitter.